1. Field of the Invention
The invention relates to a vehicular power transmitting apparatus.
2. Description of the Related Art
A transaxle type vehicular power transmitting apparatus is known in which i) a planetary gear set that forms a shifting mechanism, ii) a differential mechanism for left and right drive shafts, and iii) driving means for driving an input rotating element of that vehicular power transmitting apparatus, are all housed in a transmission case.
In addition, a front-drive power transmitting apparatus for a four-wheel-drive vehicle is also known in which a motor/generator that capable of generating electricity using power from an engine is provided separate from a driving motor, and which includes a first planetary gear set for reducing output from the driving motor, and a second planetary gear set that serves to distribute power from the engine between the motor/generator and a counter gear.
A vehicular power transmitting apparatus described in Japanese Patent Application Publication No. 8-48164 (JP-A-8-48164), for example, is such that a motor shaft and left and right driveshafts are arranged on the same axis. In addition, a spline coupling portion is provided which is connected in series in the axial direction to a toothed portion of a sun gear of the planetary gear set and is spline connected to a rotor shaft of a motor. Accordingly, the toothed portion of the sun gear can be small so a planetary gear reduction mechanism with a high reduction ratio can be realized and the motor can be reduced in size.
Also, vibrations from the planetary gear set, motor noise, or vibrations from bearings and the like tend to travel through the carrier to the case, and depending on the structure of the case, the vibrations that are transmitted to the case may be amplified, causing significant vibration and noise. Therefore, in order to prevent this, Japanese Patent Application Publication No. 2005-308094 (JP-A-2005-308094) describes a support structure for a rotating member designed to suppress vibrations at portions of the case which have low rigidity from being amplified by providing an annular protruding portion that forms asperities on an inner periphery of a hole through which a motor output shaft passes, and engaging the carrier which serves as the output element of the planetary gear set with that protruding portion on the inner periphery.
A vehicular power transmitting apparatus such as that described above is expected to be effective in inhibiting the amplification of vibrations by the case, by increasing the rigidity of the case around the planetary gear set. However, in cases such as when the input shaft and the output shaft of the planetary gear set are not on the same axis, gear noise from the teeth surfaces of the pinion gears and the sun gear, which are rotating at high speed, striking unevenly may be transmitted to the case and amplified. Also, motor noise and noise from the bearings may also be transmitted to the case by the planetary gear set and amplified.
In particular, in the front-drive power transmitting apparatus for a four-wheel-drive vehicle such as that described above, there are a plurality of planetary gear sets, which have become increasingly smaller as a result of the demand for compactness, as well as two motors so the attenuation effect of vibration and noise by the case is insufficient.